Porting arrangement for hydraulic pumps and motors



July 28, 1959 B. H.'LUNDGREN ETAL 2,896,546

PORTING ARRANGEMENT FOR, HYDRAULIC PUMPS AND MOTORS Filed Aug. 9, 1955 sSheets-Sheet 1 B. H. LUNDGREN ET AL 2,396,545

PORTING ARRANGEMENT FOR HYDRAULIC PUMPS AND MOTORS Filed Aug. 9, 1955July 28, 1959 I 3 Sheets-Sheet 2 l ifiruaemurzcyren PORTING ARRANGEMENTFOR HYDRAULIC PUMPS AND MOTORS Filed Aug. 9, 1955 July 28, 1959 B. H.LUNDGREN ET'AL 3 Sheets-Sheet 3 FIZZ '5 rates PORTING ARRANGEMENT FORHYDRAULIC PUMPS AND MGTQRS Application August a, 1955, Serial N0.527,356

11 Claims. (.Cl. 103-162 This invention relates to hydraulic pumps andmotors and, more particularly, to a porting arrangement for hydraulicpumps and motors.

A general object of this invention is to provide a new and improvedporting arrangement for hydraulic pumps and motors.

Another object of this invention is to provide a hydraulic pump whereinthe intake and discharge ports are disposed in a new and improvedarrangement so as to improve the performance thereof.

Another object of the invention is to provide a new and improvedrotating barrel type hydraulic pump or motor wherein the intake anddischarge ports are arcuately-shaped and eccentrically disposed withrespect to the axis of the rotating barrel.

Another object of this invention is to provide a new and improvedvalving arrangement for a rotating barrel type pump or motor wherein theintake and discharge kidneys are arranged with respect to the axis ofrotation of the barrel so that cylinder ports formed in the barrel areopened and closed tangentially.

Another object of this invention is to provide a new and improvedporting arrangement for a hydraulic pump or motor having a rotatablecylinder block wherein the intake and discharge arcuately-shaped portsare eccentrically disposed with respect to the axis of the cylinderblock so that cylinder ports formed in the cylinder block are opened tothe arcuately-shaped ports tangentially.

A further object of this invention is to provide in a hydraulic pump ormotor having a rotatable cylinder block provided with a plurality ofcylinders and cylinder ports axially formed therein in an annular rowwith each cylinder having a piston reciprocable therein, a new andimproved porting arrangement including an intake and a discharge portshaped and arranged relative to the axis of the cylinder block so as toopen and close the cylinder ports in a manner wherein the area of theintake and discharge ports open to the cylinder ports varies directlywith the rate of movement of the pistons in the cylinders for any speedof rotation of the cylinder block.

Other objects and advantages will become apparent from the followingdetailed description taken in connection with the accompanying drawings,in which:

Fig. 1 is a vertical sectional view of a hydraulic pump incorporating anembodiment of the invention; 6

Fig. 2 is an elevational view of the left end of Fig. 1;

Fig. 3 is a schematic view taken generally along line 33 of Fig. 1showing one symmetrical arrangement of eccentrically disposed intake anddischarge kidney ports;

Fig. 4 is a schematic view similar to Fig. 3 showing another symmetricalarrangement of intake and discharge kidney ports;

Fig. 5 is a schematic view similar to Fig. 3 showing an arrangement ofintake and discharge kidney ports of different sizes; and

Fig. 6 is a schematic view similar to Fig. 3 showing another arrangementof intake and discharge kidney ports.

While the invention is herein described with reference 2,896,546Patented July 28, 1959 ice to several embodiments, it is not intended tolimit the invention to the specific forms and arrangements shown, itbeing contemplated that various changes may be made by those skilled inthe art without departing from the spirit and scope of the invention aspointed out in the appended claims.

A hydraulic pump of the type with which this invention is well adaptedto be utilized is shown in Fig. 1, and includes a casing 2, a shaft 4rotatably mounted in bearings 6, 8 and 10 mounted in the casing 2, and abarrel type cylinder block 12 splined to the shaft 4 at 14 so as to berotatable therewith. The cylinder block 12 has formed therein an annularrow of axial cylinders 16, each of which has a piston 18 reciprocablymounted therein constantly urged by a spring 20 against a tiltable camplate 22. As the cylinder block 12 is rotated by the shaft 4, thepistons 18 are moved in their discharge strokes as a result of theirengagement with the tilted cam plate 22, the ends of pistons 18 beingrounded to form part of a ball and socket connection to slippers 23which slidably engage the cam plate 22. The length of the stroke of thepistons 18 is determined by the angle of the cam plate 22 which may bevaried by a control piston 24 slidable in a cylinder 26 formed in thecasing 2, the position of the control piston 24 being determined bymeans including a control valve 28.

A pair of cylinder ports 30 (Figs. 1 and 3) extend be tween eachcylinder 16 and a flat end face 32 of the cylinder block 12. A portplate 34 is secured to one end of the casing 2 and has a flat end face36 in contact with the face 32 of cylinder block 12. The pump casing 2is provided with a fluid inlet 38 and a fluid outlet 46, shown in Fig.2.

Referring now to Fig. 3, an arcuate or crescent-shaped intake port orkidney 42 and an arcuate or crescent-shaped discharge port or kidney 44are formed in the flat end face 36 of the port plate 34. The kidneys 42and 44 communicate through appropriate passages (not shown) with thepump inlet 38 and the pump outlet 40, respectively. When the cylinderblock 12 is rotated by the shaft 4, the cylinder ports 30 communicatealternately with the intake kidney 42 and the discharge kidney 44 sothat fluid is admitted into and then discharged under pressure from thecylinders 16, thus, providing the well known fluid pumping action.

In the operation of hydraulic pumps or motors of the rotating barreltype, the fluid pressure within the cylinders changes from low to highpressure at the crossover between the two kidneys. Thus, when the deviceis operated as a pump, fluid under low pressure is admitted into thecylinders 16 from the intake kidney 42, but the fluid within thedischarge kidney 44 is under high outlet pressure. If the fluid withinthe cylinders 16 is suddenly exposed to the pressures in the dischargekidney 44, noise may result, particularly where the cylinders 16 are notcompletely filled or where the fluid contains entrapped air. Air bubbleswill be collapsed immediately upon exposure to outlet pressure, and suchcollapse is often accompanied by both noise and wear on the pump parts.

According to the present invention, however, the kidneys 42 and 44,particularly the discharge kidney 44, are so arranged as to provide agradual opening of the cylinder ports 30 to the discharge kidney 44, andin the preferred embodiments, the rate of opening of the cylinder ports30 to the discharge kidney 44 and the extent of the opening iscorrelated with the speed of movement of the piston 18 in the cylinder16 so as to provide the minimum opening when piston speed is at aminimum, and a maximum opening at the point where the piston 18 istravelling at its maximum speed.

By arranging the discharge kidney 44 so that it opens to the cylinderports 30 tangentially thereof, a smooth transition to high pressure canbe achieved with the resulting elimination of noise and a quieteroperation of the pump. A simple. way of achieving this tangentialopeningis shown in Fig; 3/wherein the discharge kidney 44 is formed so that theouter edge 45 lies along a circle centered at the axis of rotation a ofthe cylinder block 12 and has a' radius equal to the distance from theaxis a to the outer edge of the cylinder ports 3t), If the inner edge 47of the discharge port 44 be so proportioned as to lie along a circlecentered at point c (ie on the opposite side of the axis of rotation:1), the cylinder ports 30 will be opened to the discharge kidney 44 inthe manner illustrated in Fig. 3, where the opening to the dischargekidney 44 from the cylinder ports 30 is tangential to the ports andprogresses'thereacross.

Referring again to Fig. 3, it will be noted that both the intake anddischarge kidneysAZ and 44haveb'een formed in the manner just described,and the leading and trailing ends 46 and 43 of the intake kidney 42 andthe corresponding ends 50 a'ndSZ of the discharge kidney 44 are soformed as to terminate outside oft he circle of rotation (indicated by-b )--of the cylinder ports 30. For the purpose of describing theopening and closing of the cylinder ports by the discharge kidney 44,representative positions of the cylinder-ports 30' and Eilfof one of thecylinders 16' are indicated at A, B, C, D-andE. In the crossoverposition indicated at A,it' will be noted that the cylinder port 30 ofone of the cylinders 16' has just left the trailing end 48 of the intakekidney 42 tangential ly to the outer periphery of the port 30' and theadjacent cylinder port 39 is just about to be opened to the leading end50 of the discharge kidney 44 tangentially to the outer periphery of theport 30". In position A, the area of thecylinder ports 30 and'30 open tothe kidneys 42 and 44 is zero and the rate of movement of the piston 18is zero, the piston '18 having reached the end of its stroke in thecylinder 16" so that'the cylinder 16 is filled with fluid. As thecylinder block 12 is rotated to move the cylinder ports 30' and .30"from the position illustrated at A, the leading cylinder port 30' isopened to the discharge kidney 44, with such opening taking place alonga line substantially tangent to the cylinder port 30". This gradualtangential opening of the cylinder port 30" continues until the outeredge 45 of the kidney 44 becomes tangent to the outer periphery of thecylinder port 39', which condition exists during a substantialportion'of the time the'cylinder port 30" is in communication with thedischarge kidney 44. The trailing cylinder port St? is openedtangentially by the discharge kidney 44 in the same manner. In theposition indicated at B, the area of the cylinder ports 30 and 30" opento the discharge kidney 44 has been substantially increased and the rateof movement of the piston 18 has increased directly there.

with. In the position indicated at C, the cylinder ports 30 and 30" areapproaching the midpoint of the discharge kidney 44 where the area ofthe cylinder ports 30 and 30 open to the discharge kidney 44 becomes amaximum, the inner edge 48 of the discharge kidney 44 being tangent totheinner peripheries of the cylinder ports 30 and 30", and the rate ofmovement of the piston 18 in its discharge'stroke in the cylinder 16becomes a maxi mum. In the position indicated at D, the area of thecylinder ports 30' and 30" open to the discharge kidney 44 has decreasedand the rate of movement of the piston 13 in the cylinder 16' hasdecreased directly therewith. In the position indicated at E, thecylinder ports 30 and 30-" are approaching the trailing end 52 of thedischarge kidney 44and the area of the "cylinder ports '30 and 30";opento the discharge kidney 44 has substantially decreased, the rate ofmovement of the piston 18 approaching the other end of its dischargestroke decreasing directly'therewith- As the cylinder ports 30' and 30"arerotated out of communication with the discharge kidney 44 and intocommunication with the intake kidney. 42 the --cylinder ports 30' and30" are opened and closed tangentially to their outer peripheries in thesame manner by the intake kidney 42.

Another embodiment of this invention is shown in Fig. 4 wherein anintake kidney 42a and a discharge kidney 4411 are *formed in. a portplate 34a so that the leading ends 4601 and 50a, respectively, thereofand the trailing ends 4811 and 52a, respectively, thereof are disposedwithin the circle of rotation (indicated by .b)' of the centers of thecylinder ports 3%. In this embodiment it will he noted that the inneredge 47a of the discharge kidney 44a lies along a circle centered at theaxis of rotation a of the cylinder block 12 and having a radius equal tothe distance from the axis a to the inner peripheries of the cylinderports 34. With the outer edge 45a of the discharge kidney 44a lying on acircle having a center cl which is spaced from the axis a approximatelya distance equal to the diameter of the cylinder ports 39 and toward thedischarge kidney 44a, the cylinder ports 30 are opened and closedtangentially to their inner peripheries by the discharge kidney 44ainsubstantially the same manner as described with respect to thearrangement of Fig. 3. In this arrangement, the intake kidney 42a isformed in the same manner as is the discharge kidney 44a so that theinner edge 49:: of the intake kidney 42a is tangent to the innerperipheries of the cylinder ports 30 during a substantial portion of theperiod the cylinder ports 30 are in communication with the intake kidney42a. 7 d

An embodiment of this invention wherein the two kidneys differ somewhatin size and shape is shown in Fig. 5a The discharge kidney 441) isformed substantially identical to the discharge kidney 44 of theembodiment shown in Fig. 3, the outer edge 45b lying on a circle havingits center on the axis a and a radius equal to the distance between theaxis a and the outer periphcries of the cylinder ports 3t) and't'neinner edge 47]) lying on a circle having a center 02 spaced from theaxis a away from the discharge kidney 44b, as with the center ,c of Fig.3. In this arrangement, the intake kidney 42b is formed substantiallyidentical to the intake kidney 42a of the embodiment shown in Fig. 4, aninner edge 4% of the intake kidney 42blying on a circle having itscenter on the axis of rotation a of the cylinder block 12 and a radiusequal to the distance between the axis a and the inner peripheries ofthe cylinder ports 30 and an outer edge $11; lying on a circle having acenter d2 spaced from-the axis a toward the intake kidney 425]. With thearrangement shown in Fig. 5 the cylinder ports 30 are openedtangentially to their peripheries by the kidneys 42b and 44brespectively substantially the same asdescribed with respect tothearrangements of Fig. 4-and Fig.3. The intake kidney 42b has theleading end] 4612 and the trailing end 43b,disposed inside the circle ofrotation (indicated by b) of the centers of the cylinder ports 36, thecylinder ports 3% thus being opened and closed tangentially to theirinner peripheries by the inlet kidney 421;. The discharge kidney 44bopens and closes the cylinder ports 30 tangentially/to their outerperipheries, the leading end Stib and the trailing end 52% thereof beingdisposed outside the circle of rotation b of the centers ofcylinderPorts30. A further embodiment of the invention is shown .in thearrangementcf Fig. 6 wherein an inlet kidney 420 andan outlet kidney 440are arranged so that leading ends 460 and 500, respectively, thereof aredisposed inside the circle of rotation (indicated byb) of the centersofcylinder ports 30 and trailing ends 480 'and52c, respectively, thereofare disposed outside the circle of rotation (indicated by [2). Thedischarge kidney. 44c has an' inner edge comprising 'a leading portion47c and a. trailingportion 47c and an outeriedge comprising-aleading-portion 45cand.a trailing portion 450. The edge portions; 47cand 45c. each define an arc havassaaie ing a center on the axis ofrotation a of the cylinder block 12, the radius of the arc of theportion 470 being equal to the distance from the axis a to the innerperipheries of the cylinder ports 30 and the radius of the arc of theportion 450 being equal to the distance from the axis a to the outerperipheries of the cylinder ports 30. The inner edge portions 470'defines an arc having a center 03 spaced 'from the axis a and away fromthe discharge kidney 44c while the outer edge portion 45c defines an arehaving a center c3 spaced from the axis a andtoward the discharge kidney440. Likewise, the intake kidney 420 has an inner edge comprising atrailing portion 49c and a leading portion 490' and an outer edgecomprising a trailing portion 510 and a leading portion 51c. The edgeportions 510 and 490 each define arcs having centers on the axis a andradii equal to the distances from the axis a to the outer peripheries ofthe cylinder ports 30 and the inner peripheries of the cylinder ports30, respectively. The inner edge portion 490 defines an are having acenter d3 spaced from axis a and away from the intake kidney 42c and theouter edge portion 510' defines an arc having a center 113' spaced fromaxis a approximately the diameter of the cylinder ports 30 toward theintake kidney'42c. With this arrangement, the cylinder ports 30 areopened tangen .tially to their inner peripheries by the leading ends 46cand 50c and closed tangentially to their outer peripheries by thetrailing ends 480 and 52c.

As ShOWn in Figs. 4, 5 and 6, where the leading ends 46a, 46b, and 460of the intake kidneys 42a, 42b and 42c are disposed inside the circle ofrotation (indicated by b) of the centers of the cylinder ports 30, thecylinder ports 30 are opened tangentially to their inner peripheries bythe leading ends of the intake kidneys so as to aid in filling thecylinders '16 inasmuch as the centrifugal force of rotation of the fluidentering the cylinder ports 30 is added to the intake pressure of thefluid.

It is noted that this invention is not limited to the embodiments ofporting arrangements shown and described herein, but includes otherpossible arrangements of kidney ports wherein the cylinder ports areopened and closed tangentially to their peripheries by the kidney ports,and wherein the area of the kidney ports open to the cylinder portsvaries directly with the rate of movement of the pistons in thecylinders without regard to the speed of the rotating cylinder block.

While an understanding of the operation of control valve 28 is notnecessary to an understanding of the present invention, a description ofthe valve will facilitate an understanding of the pump operation as awhole. It should be understood, however, that the valve 28 is .not anecessary element in a pump utilizing the present invention, but may beomitted or replaced by other controls of the same or a different type.

In a preferred application, the control valve 28 is utilized to vary thedisplacement of the pump as the speed of the drive shaft varies in orderthat the volumetric pump output may be maintained at a constant value,for example, to drive a hydraulic motor at a constant speed. In order toattain this purpose, the cam plate 22 normally assumes a minimumdisplacement position (not shown) by virtue of the action of gravity onthe plate and by the plurality of individual piston springs 20. When thepump is first started, the cam plate occupies such a minimumdisplacement position, and at that time valve 28 is effective to admitfluid under pressure to the control chamber 26 to urge the piston 24toward the right as viewed in Fig. 1 thereby to shift the cam plate 22toward a maximum displacement position as illustrated in Fig. 1. As thepresure and flow of fluid delivered by the pump increase after operatingspeed is attained, valve 28 will reduce the flow of fluid to controlchamber 26, or even connect the chamber to drain in order that the camplate may return toward minimum displacement position, this 6 beingdesirable when the speed of the pump drive shaft increases unavoidably,if the volumetric output is to be maintained constant.

The valve 28 includes a valve bore 60 having an outer valve member 61 inthe form of a sleeve slidable therein, and an inner valve member 62slidable in valve member 61. Valve member 61 provides the displacementcontrol referred to, while valve member 62 provides an overpressurerelief control. Sleeve 61 is urged upwardly in the bore 60 by a spring64 while the valve member 62 is urged upwardly in sleeve 61 by a spring65 toward a snap ring 66 retained in the upper end of sleeve 61.

Control fluid under pressure is admitted to the chamber 26 through aconduit 68 adapted for connection with a port 69 in sleeve 61 when thesleeve occupies a position slightly above that illustrated in Fig. 1.When the sleeve 61 is so positioned, the port 69 therein is adapted forcommunication with a port 70 in valve member 62 when the latter is movedupwardly against the snap ring 66. This position, with both valvemembers in their uppermost positions, is the normal condition of thecontrol valve when the pump is started. Under these conditions, thehollow interior of valve member 62 communicates through a port 71 withthe valve bore 60 which in turn has a port 72 leading outwardlytherefrom. a

Port 72 functions to supply control fluid to the valv bore 60 fordelivery to control chamber 26, and the fluid admitted through the port72 also acts against the lower ends of the valve members to urge bothupwardly. At the upper end of the bore 60 a port 73 opens into the borefor admitting pressure fluid to act against the upper end of the valvemembers.

Preferably, in order to maintain a constant volumetric flow the pumpoutlet includes a restrictive orifice (not shown), and a conduitconnects the port. 72 with the pump outlet downstream from the orificewhile a sepa rate conduit connects the port 73 with the pump outletupstream of the orifice. In this manner the pressure drop across theorifice controls the position of the valve.

In operation, when the pump is started control fluid flows to thechamber 26 through port 72, bore 60, port 71, port 70, port 69 andconduit 68 to urge the piston 24 toward the right, increasing pumpdisplacement. As flow increases through the pump outlet, pressure risesupstream of the orifice referred to, and when the desired pumpdisplacement is attained the pressure in port 73 and the upper end ofbore 60 urges the valve members 61 and 62 downwardly to a positionwherein port 69 is blocked, substantially as illustrated in Fig. l, tohold piston 24 and cam plate 22 at the desired position.

In the event of a decrease in pump speed the pressure drop across saidorifice decreases, and the valve members move upwardly to connect ports72 and 69 and increase pump displacement. In the event of an increase inpump speed, the pressure drop across said orifice increases, the valvemembers move downwardly and conduit 68 is connected to drain through anouter annular groove 75 on the sleeve 61 and through a drain passage 77leading from the bore 66, thereby to permit a reduction in the pumpdisplacement.

Valve member 62 provides an overpressure relief control whereby, whenthe pressure in the pump outlet increases to an excessive value,pressure acting against the larger upper endof valve member 62 issuflicient to overcome the pressure of spring 65 and fluid actingagainst the smaller lower end of member 62, moving the valve member 62downwardly from the position illustrated in Fig. l to a position whereinan outer annular groove 78 on valve member 62 connects conduit 68 andport 69 to drain through a port 80 in the valve sleeve 61, and drainpassage 77.

We claim:

1. In a hydraulic pump or motor having a rotatable cylinder blockprovided with a plurality of cylinders formed axially therein, acylinder port for each cylinder and opening to an end face of thecylinder block and a piston reciprocable in each of said cylinders, aporting arrangement comprising; a port plate disposed adjacent the endface of the cylinder block and having an intake kidney and a dischargekidney formed therein, said kidneys being generally crescent-shaped andpositioned in said port plate to communicate alternately with thecylinder ports upon rotation of the cylinder block, the inner and outeredges of at least one of said kidneys defining arcs of circles on saidport plate, one are having a center disposed on the axis of rotation ofsaid cylinder block and a radius extending to one peripheral edge of thecylinder ports and the other are having a second center spaced from theaxis of rotation of said cylinder block and a radius equal to thedistance between said second center and the other peripheral edge of thecylinder ports when positioned at the midpoint of said kidney. 7

2. In a cam plate type hydraulic pump or motor having a rotatablecylinder block provided with a plurality ofcylinders formed axiallytherein, a cylinder port for each cylinder and opening to an end face ofthe cylinder block and a piston reciprocable in each of said cylinders,a porting arrangement comprising; a port plate disposed adjacent the endface of the cylinder block and having an intake kidney and a dischargekidney formed therein, said kidneys being generally crescent-shaped andpositioned in said port plate to communicate alternately with thecylinder ports upon rotation of the cylinder block, the inner and outeredges of the discharge kidney defining two circular arcs havingapproximately equal length radii, one of the arcs having a centerdisposed on the axis of rotation of said cylinder block with the radiusextending to one peripheral edge of the cylinder ports, the other arehaving a center spaced from the axis of rotation of the cylinder block adistance approximately the diameter of the cylinder ports.

3. In a hydraulic pump or motor having a rotatable cylinder blockprovided with a plurality of cylinders formed axially therein, acylinder port for each cylinder and opening to an end face of thecylinder block and a piston reciprocable in each of said cylinders, aporting arrangement comprising; a port plate disposed adjacent the endface of the cylinder block and having an intake kidney and a dischargekidney formed therein, said kidneys being generally crescent-shapedand'positioned in said port plate to communicate alternately with thecylinder ports upon rotation of the cylinder block, the inner edgesofthe kidneys defining first arcs having centers disposed on the axis ofrotation of the cylinder block and radii extending to the inner edges ofthe cylinder ports, the outer edges of the kidneys defining arcs havingradii equal to the radii of said first arcs and centers spaced from theaxis of rotation of the cylinder block toward the kidneys a distanceapproximately the diameter of the cylinder ports.

4. In a hydraulic pump or motor having a rotatable cylinder blockprovided with a plurality of cylinders formed axially therein, acylinder port for each cylinder and opening to an end face of thecylinder block and a piston reciprocable in each of said cylinders, aporting arrangement comprising; a port plate disposed adjacent the endface of the cylinder block and having an intake kidney and a dischargekidney formed therein, said kidneys being generally crescent-shaped andpositioned in said port plate to communicate alternately with thecylinder ports upon rotation of the cylinder block, the inner edge ofthe intake kidney and the outer edge of the discharge kidney definingarcs of unequal radii having centers disposed on the axis of rotation ofthe cylinder block, the arc defined by the inner edge of the intakekidney having a radius extending to the inner peripheries of thecylinder ports, the arc defined by the outer edge of the dischargekidney having a radius extending to the .outer peripheries of thecylinder ports, the outer edge of the intake kidney defining an arehaving a center spaced from the axis of rotation and toward the intakekidney and a radius such that the midpoint of the outer edge of theintake kidney is tangent to the outer peripheries of the cylinder ports,the inner edge of the discharge kidney defining an are having a centerspaced from the axis of rotation and away'from the discharge kidney anda radius such that the midpoint of the inner edge of the dischargekidney is tangent to the inner peripheries of the cylinder ports.

5. In a hydraulic pump having a rotatable cylinder block provided withan annular row of cylinders formed axially therein and cylinder portsopening to an end face of the cylinder block, a porting arrangementcomprising; a port plate having a face contacting the end face of thecylinder block and an intake and a discharge kidney formed in the faceof the port plate and adapted to communicate alternately with thecylinder ports upon rotation of the cylinder block, said kidneys. beingso arranged with respect to the axis of rotation of the cylinder blockthat the cylinder ports are opened and closed tangentially to theperipheries thereof, the intake kidney being arranged to open thecylinder ports tangentially to the inner peripheries thereof to add thecentrifugal force of rotation to input pressure to aid in filling thecylinders with fluid.

6. The combination of claim 5, wherein the intake kidney is arranged toclose the cylinder ports tangentially to the inner edges thereof.

7. The combination of claim 1, wherein the inner edge of the intakekidney defines a first are having its center disposed on the axis ofrotation of the cylinder block and a radius extending to the inner edgesof the cylinder ports, and wherein the outer edge of the intake kidneydefines an are having a radius equal to the radius of said first arc anda center spaced from the axis of rotation of the cylinder block towardthe intake kidney a distance approximately equal the diameter of thecylinder p r w 8'. In a hydraulic pump or motor having a rotatablecylinder block provided with a plurality of cylinders formed axiallytherein, a cylinder port for each cylinder and opening to an end face ofthe cylinder block and a piston reciprocable in each of said cylinders,a porting arrangement comprising; a port plate disposed adjacent the endface of the cylinder block and having an intake kidney and a dischargekidney formed therein, said kidneys being generally cresent-shaped andpositioned in said port plate to communicate alternately with thecylinder ports upon rotation of the cylinder block, the inner edge ofthe intake kidney and the outer edge of the discharge kidney definingarcs of unequal radii having centers disposed on the axis of rotation ofthe cylinder block, the arc defined by the inner edge of the intakekidney having a radius extending to the inner edges of the cylinderports, the arc defined by the outer edge of the discharge kidney havinga radius extending to the outer edges of the cylinder ports the outeredge of the intake kidney defining an are having a center spaced fromthe axis of rotation and toward the intake kidney by an amountapproximately equal the diameter of the cylinder ports and a radius suchthat the midpoint of the outer edge of the intake kidney is tangent tothe outer edges of the cylinder ports, the inner edge of the dischargekidney defining an are having a center spaced from the axls of rotationand away from the discharge kidney and a radius such that the midpointof the inner edge of the discharge kidney is tangent to the inner edgesof the cylinder ports and the ends of the inner edge of the dischargekidney are tangent to the outer edges of the cylinder ports.

9. In a hydraulic pump or motor having a rotatable cylinder blockprovided with a plurality of cylinders formed axially therein, acylinder port for each cylinder and opening to an end face of thecylinder block and a plston reciprocable in each of said cylinders, aporting arrangement comprising; a port plate disposed adjacent the endface of the cylinder block and having an intake kidney and a dischargekidney formed therein, said kidneys being generally crescent-shaped andpositioned in said port plate to communicate alternately with thecylinder ports upon rotation of the cylinder block, the inner and outeredges of at least one of said kidneys defining arcs of circles on saidport plate, one are being tangent to the cylinder ports at oneperipheral edge thereof, and the other are having its midpoint tangentto the cylinder ports at the opposite peripheral edge thereof and itsends tangent to the cylinder ports at said one peripheral edge thereof.

10. The combination of claim 9, wherein the discharge kidney has itsouter edge defining an arc tangent to the outer edges of the cylinderports, and wherein the discharge kidney has its inner edge defining anarc tangent at its midpoint to the inner edges of the cylinder ports and10 tangent at its ends to the outer edges of the cylinder ports. 11. Thecombination of claim 9, wherein each kidney has its outer edge definingan arc tangent to the outer edges of the cylinder ports, and each kidneyhas its inner edge defining an arc tangent to the inner edges of thecylinder ports at the midpoint of the kidney and tangent to the outeredges of the cylinder ports at the ends of the kidney.

References Cited in the file of this patent 5 UNITED STATES PATENTSLauck et al Mar. 31, 1953

